Today's portable terminal devices have limited input, output and storage capabilities, which directly limit the usability of such conventional portable terminal devices. Due to those limitations users are forced to handle such portable terminal device with more or less effort. Whereas the limitations in output and storage capabilities will be overcome by the implementation of currently available and future technical developments becoming standard, the limitation in the input capability is the most challenging task in the view of technical innovation and development. In particular, the overcoming of the limited input capability of the portable terminal devices is difficult due to the fact that the number of input means is bounded by dimension and weight of those terminal devices. Typically solutions, which are already developed for instance with respect to desktop terminal devices, cannot be migrated to the field of portable terminal devices due to the given boundaries of the portable terminal device such as those mentioned above.
Several concepts, which enable context awareness of portable terminal devices, are currently under development to simplify the handling of those devices having limited input capability. In principle, context awareness designates typically the tailoring of a user interface of a portable terminal device to currently present environmental conditions; i.e. the user interface of a portable terminal device can be automatically adapted to the environmental conditions by for example presenting available choices or choices possibly desired by the user.
Basically, two state of the art approaches for context awareness in the above-enlightened sense shall be presented. Portable terminal devices may implement context sensors such as position measuring sensors or other sensors for detecting physical context properties. On the basis of context information resulting from such sensors such portable terminal devices are able to react correspondingly. In the second approach several context providing (serving) entities distributed in the environment serve for providing context information to portable terminal devices adapted to acquire the context information therefrom; i.e. such portable terminal devices collect the context information and react thereto on the basis of an analysis of the collected context information.
Both presented approaches suffer from significant disadvantages relating to costs, scaling, flexibility and configurability. In detail, in accordance with the first approach, portable terminal devices implementing sensors for detecting and sensing context information requires supplementary information to be retrieved since the sensed information is typically not sufficient for an adequate reaction of such portable terminal devices. However, the retrieving of such supplementary information on the basis of the sensed context information is problematic or even impossible, when considering that all supplementary information should be stored centrally in view of usability aspects. The distributed provision of the context information as purposed with the second approach overcomes the disadvantage of the first approach, but the provision and the maintenance of context providing entities is expensive and elaborate. Moreover, the specific provision of context providing entities dedicated for predefined purposes lack in flexibility and configurability.